1. Field of the Invention
This invention relates to weapons, and particularly to means for converting small arms weapons that use ammunition of a particular caliber into a version that will be usable for firing cartridges of a different, usually smaller caliber, while retaining the same original sighting characteristics at the completion of the conversion and without needing to replace the expensive original slide.
2. Background Information
In performing their duties, police officers, members of the military and the like generally employ small arms of relatively large caliber, such as .45 caliber. These weapons will also be of automatic or semi-automatic design, employing center fire, meaning that the firing pin will impinge on the shell along the central axis of the cartridge. Since such weapons have considerable power but are yet small in size, the amount of training required to master their proper use, particularly in achieving accurate and dependable aiming, is substantially greater than that required to learn, for example, the proper use of rifles or shotguns. With the smaller, hand held weapon, referred to hereinafter generally as a pistol, a handgun or simply a gun or firearm, skill in avoiding flinching due to the noise and recoil when the gun is fired must be acquired, specifically through learning the art of sight picturing and trigger squeeze. Such training requires spending considerable time in practice firing on a firing range, for which the ammunition required for the larger .45 caliber, 9 mm or similar sizes can be quite expensive.
For economic reasons, it would thus be useful to have a handgun of much the same size and weight, and having other features similar to the normal, large caliber handgun, but yet which fired smaller caliber and less expensive ammunition, and in fact efforts to make such adaptations have quite a long history as noted below and in the Information Disclosure Statement filed herewith. The cost of .22 caliber ammunition, for example, is only about 10% of the cost of 9 mm parabellum or .45 ACP ammunition. In order to avoid the purchase of a second handgun, it is thus a better method of decreasing costs, by easily reversible means, to convert a standard .45 or 9 mm handgun so as to fire .22 caliber ammunition. That procedure would preferably retain the weight and most of the other characteristics of the larger caliber weapon, whereby meaningful and useful practice with such a modified weapon can be carried out.
It would also be preferable to minimize, as much as possible, the cost of making that conversion. A principle cost, as exhibited by prior art methods of caliber conversion, lays in the need to replace the slide of the original Colt .45. It was thus deemed advisable to seek out whatever additional changes to the weapon would be necessary in order to allow that original slide to be retained. Among other purposes, the slide serves to extract and eject expended cartridges, so it was thought to devise means by which that process could be carried out in spite of the smaller size of the cartridges, but with the original slide still intact. That effort finally settled on the use of a sliding extractor, with the original slide remaining to carry out its other purposes such as locking the weapon “open” when all of the cartridges therein had been expended. The present disclosure shows and describes the means for so doing, while also adding a number of other new and novel features to the art of caliber conversion.
Semi-automatic handguns operate generally on the basis of one or the other of two different main principles. One of these is a “blowback” or “spent case projection” operation in which the breech block or bolt of the handgun is not physically locked to the barrel. Upon a cartridge being fired, the cartridge case is impelled backwards onto the face of the bolt or block, which is then driven to the rear at a much lower velocity than that of the bullet. When the bullet leaves the muzzle, the propelling gas is then free to leave also, and the gas pressure against the cartridge case and breech block drops instantly. However, enough momentum would have been imparted to the breech block to allow the re-loading action to continue in the absence of continued pressure.
A second main principle on which semi-automatic handguns operate is that termed “short recoil.” In this method of operation, generally used only on more powerful handguns, the barrel and breech block are mechanically locked together at the moment of firing in order to contain the high pressures involved. As the bullet is propelled down the barrel, an equal and opposite force is applied to the breech block. Under the influence of this force, the barrel and breech block begin to accelerate in the direction opposite to that of the bullet, albeit at a much lower velocity because of the greater mass of the barrel and breech block than of the bullet. After a brief travel during which time the bullet has exited the barrel and the pressure has dissipated, the breech block is unlocked from the barrel and allowed to continue rearward while the movement of the barrel is halted. As the breech block continues rearward, the fired cartridge case is extracted and expelled, and the breech block can return to place a fresh cartridge in the chamber. This is the principle of operation of the M1911 .45 caliber pistol or “Colt .45” to which the present invention has been specifically applied.
A third main principle on which semi-automatic arms operate, although not usually applied to hand guns, is that of gas operation in which for greater force a portion of the propelling gas is tapped off from the barrel via a port and then directed into a cylinder containing a piston that moves rearward in response to that gas pressure. The piston is in turn coupled to the breech block, which is then forced to open and re-load the handgun. In some variations, no cylinder or piston will be used, and the gas is allowed to impinge directly on the bolt or similar mechanism. The U.S. Army's M1 carbine employs this gas operated principle, as does the present invention. Analogous uses of the present invention on other handguns of the same general type are of course intended to be encompassed within the claims appended hereto.
Starting with any of these principles, the development of any adaptation of the handgun that would permit the use of lower caliber ammunition requires taking account of the various steps involved in the standard self-loading or semi-automatic firing processes, noting that the design considerations applicable to the larger and the smaller caliber guns can be quite incompatible. Large caliber, self-loading handguns nearly always employ a locked breech mechanism to contain the high chamber pressures produced on firing. This structure, particularly with the Colt .45, forms a short recoil system wherein the barrel and breech block are locked together during an initial recoil period that follows the firing of a cartridge, and after the resultant breech pressure has subsided the barrel and breech block are uncoupled to allow the breech block to recoil away from the barrel, eject the expended cartridge, and load a fresh cartridge. Such systems necessarily employ strong and massive recoiling parts in order to contain the high pressures generated and to slow the acceleration of the moving parts so that they do not move to the “unlock” position until enough time has passed for the chamber pressure to subside. With the larger caliber ammunition, sufficient force to operate the full “reload” mechanism is readily available from firing the cartridge because of the powerful pressures generated.
Conversion to the use of lower caliber ammunition thus means that the levels of pressure characteristic of the higher caliber ammunition are no longer available. Because of the lighter weight of the smaller caliber handguns, it is indeed the practice in the designs of the lower caliber handguns that have less weighty parts to have such weapons operate on the less powerful blowback principle. In converting the larger handgun to use lower caliber ammunition, some means must then be employed to obtain the forces necessary for movement of the heavy parts of the original handgun. Advantageously, the adaptation of such a handgun to use smaller caliber ammunition would be carried out so that the weapon would use the gas pressure principle in a way that will function properly when necessarily using the lower pressure that is available from that lower caliber ammunition.
The breech face, that during the chambering portion of the firing cycle is used to rake the next cartridge out of the magazine and into the chamber, is large in order to support the base of the large .45 cartridge during firing. The breech face also contains a firing pin located along the central axis of the barrel so as to detonate the center-fire cartridge, and an extractor claw is located radially away from the barrel axis to extract fired or unfired cartridge cases from the chamber. The exact radial position of the extractor is dictated in part by the diameter of the cartridge. Generally, there is also a fixed ejector mounted to the main frame in a position as to impact the edge of the base of the recoiling cartridge case being carried rearward by the extractor mounted on the breech face, and at a point approximately diametrically opposite to the extractor. The impact of the moving cartridge case on the ejector serves to generate a moment to the cartridge case about a transverse axis of the extractor claw, which moment then causes the empty cartridge case to pivot sideways and be expelled from the gun. Of course, the radial position of the ejector relative to the barrel axis is also dictated by the diameter of the cartridge. The return cycle of the breech block is normally powered by a spring that has been compressed during the recoil portion of the cycle. This spring is relatively heavy in order to store enough energy to return the heavy recoiling parts and to strip the next cartridge from the magazine.
With reference to conversions such the present one in which a change is made not only in caliber but also to accommodate the rim fire cartridge of the .22 instead of the center fire cartridge in the .45, although not used in the principal prior art reference herein noted below, it is also known to use an eccentric chamber/bore in the adapted firearm so that a center-firing mechanism will align the firing pin of the handgun with the rim of the .22 rim fire cartridge, this technique being seen most often in single shot adaptors and firearms, e.g., in the Stevens Crackshot single shot rifle. Another adaptation feature known in the art is the use in the adapted firearm of a magazine that is inwardly tapered back-to-front (towards the muzzle) so as to allow more nearly parallel stacking of the rimmed .22 cartridge, as found, for example, in the .22 caliber Smith and Wesson 422.
More specific background from the prior art will now be set out with reference to the M1911 Colt .45 in particular, as shown in FIG. 1, which is a perspective, exploded view of those portions of a Colt .45, designated herein as Colt .45 pistol 10, that pertain to the conversion comprising the invention. The operation of this .45 caliber handgun and a method of conversion thereof to .22 caliber is described in U.S. Pat. No.2,090,657 issued Aug. 24, 1937, to Williams, which patent by this reference is hereby incorporated herein as though fully set forth. That is, FIG. 1 shows those portions of the Colt .45 pistol as described in the Williams '657 patent as pertain specifically to the present invention, but not necessarily to the Williams '657 conversion. Versions of the “Colt .45” are also shown in the original patents therefor, which are U.S. Pat. No. 580,924 issued Apr. 20, 1897, to J. M. Browning; U.S. Pat. No. 984,519 issued Feb. 14, 1911, to J. M. Browning; and U.S. Pat. No.1,070,582, issued Aug. 19, 1913, to J. M. Browning.
Colt .45 pistol 10 comprises a frame 12, barrel 14, locking lugs 16, slide 18, slide stop 20, barrel bushing 22, recoil spring 24, spring guide 26, spring retainer 28, magazine 30 and chamber 32. FIG. 1 also shows takedown notch 34 and slide stop tang 36, that are shown again in FIG. 2 in more visible form. It can be seen that recoil spring 24 is first disposed over spring guide 26, and is contained or retained within spring retainer 28. FIG. 1 also shows breech face 38, slide grooves 40, slide stop hole 42, frame alignment hole 44, barrel bushing tang 46, magazine well 48, feed ramp 50, feed lips 52, depending rib 54, slide stop notch 56, slide hood 58, follower 60, slide stop shaft 62, pivot link 64 and firing pin 66. It may be noticed that “feed lips 52” has two lead lines in FIG. 1, which is because there are left and right feed lips 52. A listing of relevant parts in the original Browning Colt .45 pistol 10, the parts of the Williams '657 conversion kit 70, and all of the parts of the invention is given in Table I below.
In what follows, any part shown in the later figures that has a reference number less than 70 will be a part of the original Colt .45 pistol 10 that either the Williams '657 conversion kit 70 or the present conversion kit leaves in place, while FIG. 1 shows all of the relevant parts of the original Colt .45 pistol 10. The parts of the present conversion kit begin with the number 100. For purposes of easy access and better orientation to what will follow, however, the Williams '657 parts are listed here: conversion kit 70, firing pin 72, extractor 74, ejector 76, slide 78, barrel 80, floating chamber 82, magazine 84, depending rib 86, breech face 88, feed ramp 90, feed lips 92, chamber 94, and magazine depressions 96. (A part of the present invention that roughly corresponds to the Williams '657 floating chamber 82 is here termed “gas piston 108.”) Breech face 88 is formed in the Williams '657 conversion by carrying out a counter bore into slide 78, thus to provide a recess to enclose the base of the cartridge and maintain the cartridge rim in close contact with extractor 74 during the extraction. Chamber 94 is that portion of floating chamber 82 that holds the cartridge during the firing portion of the operation cycle, and as shown in FIGS. 3, 4, chamber 94 is a hole coaxially located within floating chamber 82 and sized so as to receive the cartridge closely. The roles of the other parts just listed will be set out below. Magazine depressions 96 in the side walls of the magazine serve to produce a narrow section therein to center the smaller .22 caliber cartridges. This permits the portions of the magazine on either side of these depressions to be kept at the same size as is the standard .45 caliber magazine and hence fit closely into magazine well 48.
The firing of a cartridge in Colt .45 pistol 10 causes both barrel 14 and slide 18 to be propelled rearward, and at a certain point locking lugs 16 of barrel 14 are disengaged from slide grooves 40 of slide 18 by pivot link 64 on barrel 14, whereby barrel 14 does not itself continue further, while slide 18 proceeds further rearward. Pivot link 64 is rotatably attached to the underside of barrel 14, and at the distal end thereof connects rotatably to slide stop shaft 62 of slide stop 20. As slide 18 recoils, pivot link 64 pivots around slide stop shaft 62 of slide stop 20 and pulls the rear of barrel 14 downward and out of engagement with slide 18 as barrel 14 goes through its shorter distance of movement. The rearward movement of slide 18 compresses recoil spring 24 as contained between spring guide 26 and spring retainer 28, the spent cartridge is ejected, and a new cartridge is drawn from magazine 30 in the well known manner, and that new cartridge is placed into chamber 32 as both barrel 14 and slide 18 are returned to their original positions through the expansion of recoil spring 24. (The term “slide stop” should not be taken to mean a “stop” of that rearward motion of slide 18, since that is accomplished by the compression of recoil spring 24 and ultimately by contact of slide hood 58 with the base of spring guide 26. Slide stop 20 serves instead to lock slide 18 in an “open” position upon ejection of a last cartridge, or that same process can be carried out by pressing upward on slide stop 20 at a time at which slide 18 is in the most rearward (open) position and slide stop tang 36 can engage slide stop notch 56.)
A showing of the Williams '657 conversion is accomplished in part by FIG. 3, which shows in horizontal section, as a cutaway view from the top, a Colt .45 pistol 10 that has been converted to .22 caliber cartridges by the Williams conversion kit 70. FIG. 3 shows the Williams '657 firing pin 72, extractor 74, ejector 76, slide 78, barrel 80, a vibrating member, sometimes called a floating chamber and termed herein as floating chamber 82, breech face 88, and chamber 94. Extractor 74 is a hook-like device that removes the empty cartridge case from floating chamber 82, and the manner of so doing in the invention will be explained below. Ejector 76 is a “drop-in” part that does not move but is connected into frame 12 under barrel 80 and floating chamber 82, sitting just above magazine 84 on the left side of the firearm, to the left of depending rib 86 of the Williams '657 conversion slide 78. Ejector 76 acts as a “shoulder” against which a spent case that is being withdrawn from floating chamber 82 by extractor 74 will strike, thus causing that spent case to be ejected sideways from the weapon, and the corresponding process in the invention will also be explained below.
The labeled parts shown in FIGS. 4–5 extend beyond those in FIGS. 1–3, and show more detail as to the firing and extractor portions of the Williams '657 patent, specifically including the Williams '657 magazine 84 and depending rib 86. The role of each of the parts of FIGS. 1–5 will be explained below in the Detailed Description of the Invention, for purposes of comparison with FIG. 6 that shows the various parts of conversion kit 100 that constitutes the present invention.